I am starting my second app and one of the requirements of the customer is that users will receive a notification when they should make a new appointment or purchase new maintenance products for their medical instruments.
Since this is an app with medical (so very personal) information I'd like to avoid using third party services. The notifications must always been shown, even when the app is not active. So I was looking for push notifications but those seem (always) to rely on third party cloud services.
One option is to simply create an agenda item with an alarm, but are there other, more elegant ways to get the user's attention, even if the app is not running?